Study of Earthquake Disaster Prevention of Waterfront

本研究的成果总结如下：(I)根据以往地震中填海造地生命线性能的研究现状，指出应从断层附近的地震运动、软土地基的动力响应、液化引起的地面位移及其对埋藏的生命线设施的影响等方面进行具体的研究，以建立日本滨水地区的抗震城市社会。(Ii)液化可对生命线结构造成多种破坏；由于地面承载能力降低而引起的建筑物的沉降和倾斜，由于液化土壤的浮力而引起的地下建筑物的漂浮，由于土压力增加而导致的码头墙和挡土墙的坍塌，路堤等土体结构的破坏，以及液化引起的地面大位移的破坏。(Iii)在日本过去的10次地震中发现了液化引起的地面位移，其名称为…比在美国更好。地表位移主要由高程较高的沙丘和天然堤防向高程较低的大江大河老溪流方向发展。1964年新泻地震时，地表最大位移超过12m。(4)地表位移大小与液化层厚度密切相关，与地表坡度无关。与液化有关的地面大位移的发生机制尚不清楚。因此，需要进行更多的地表位移时程研究、数值分析和试验研究。(V)液化引起的地表位移对地下结构物如基桩、管线等造成严重破坏。通过对破损结构的检测和试验研究，推测地下结构受到液化土体的阻力作用。(Vi)提出了在可液化土体中建造柔性围护结构以防止液化引起的地面位移的方法，并通过振动台试验验证了其有效性。较少

The summary of the results of the present research is as follows ;(i) It was pointed out based on the state of the art on lifeline performance in reclaimed ground during past earthquakes that specific research subjects such as earthquake motion in the neighborhood of fault, dynamic response of soft ground, liquefaction-induced ground displacement and its effect on buried lifeline facilities should be proceeded to create earthquake-proof urban societies in waterfronts in Japan.(ii) Liquefaction can cause several kinds of damage to lifeline structures ; settlement and tilting of structures due to reduction of bearing capacity of ground, floating of buried structures due to the buoyancy of the liquefied soil, collapse of quay walls and retaining walls due to earth pressure increase, failure of earth structures like embankment, and damage to liquefaction-induced large ground displacement.(iii) The liquefaction-induced ground displacements were found during ten past earthquakes in Japan as … More well as in United States. The ground displacements were oriented from sand dunes and natural levees with a little higher elevation towards old streams of big rivers with a lower elevation. The maximum ground displacement reached over 12 m during the 1964 Niigata earthquake.(iv) The magnitude of the ground displacement has a close correlation with the thickness of the liquefied layer, but not with the gradient of the ground surface. The mechanism of the occurrence of the liquefaction-related large ground displacement has not been clarified. Therefore, more studies on case histories of ground displacement, numerical analyses, experimental studies are required.(v) The liquefaction-induced ground displacement caused severe damage to buried structures such as foundation piles and pipelines. It was conjectured from examination of damaged structures and experimental studies that a drag force of liquefied soil was applied to the buried structures.(vi) A method to prevent liquefaction-induced ground displacement, where flexible inground walls are constructed in liquefiable soil, was proposed and its effectiveness was verified by shaking table tests. Less